Loans and Allowance for Loan Losses - Changes in allowance (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in the allowance
Beginning Balance	$ 22,174	$ 16,564	$ 15,615
Provision for loan losses	7,312	8,610	3,280
Loan charge-offs	(7,578)	(4,253)	(4,840)
Loan recoveries	2,016	1,253	2,509
Ending Balance	23,924	22,174	16,564
Unallocated
Changes in the allowance
Beginning Balance	1,177	911	1,516
Provision for loan losses	1,015	266	(605)
Ending Balance	2,192	1,177	911
Commercial
Changes in the allowance
Beginning Balance	18,656	12,841	11,666
Provision for loan losses	3,797	8,765	3,180
Loan charge-offs	(6,541)	(3,783)	(3,287)
Loan recoveries	1,623	833	1,282
Ending Balance	17,535	18,656	12,841
Commercial \| Commercial and industrial
Changes in the allowance
Beginning Balance	12,127	7,589	6,702
Provision for loan losses	5,213	6,911	3,244
Loan charge-offs	(6,540)	(3,123)	(3,287)
Loan recoveries	1,470	750	930
Ending Balance	12,270	12,127	7,589
Commercial \| Real estate construction
Changes in the allowance
Beginning Balance	250	343	480
Provision for loan losses	51	(35)	(416)
Loan charge-offs	(1)	(60)
Loan recoveries	3	2	279
Ending Balance	303	250	343
Commercial \| Commercial real estate
Changes in the allowance
Beginning Balance	6,279	4,909	4,484
Provision for loan losses	(1,467)	1,889	352
Loan charge-offs		(600)
Loan recoveries	150	81	73
Ending Balance	4,962	6,279	4,909
Consumer
Changes in the allowance
Beginning Balance	2,341	2,812	2,433
Provision for loan losses	2,500	(421)	705
Loan charge-offs	(1,037)	(470)	(1,553)
Loan recoveries	393	420	1,227
Ending Balance	4,197	2,341	2,812
Consumer \| Residential \| Real estate first mortgage
Changes in the allowance
Beginning Balance	1,156	1,411	1,126
Provision for loan losses	292	(226)	182
Loan charge-offs		(29)
Loan recoveries			103
Ending Balance	1,448	1,156	1,411
Consumer \| Residential \| Real estate junior lien
Changes in the allowance
Beginning Balance	805	902	907
Provision for loan losses	1,825	(171)	247
Loan charge-offs	(465)	(133)	(1,124)
Loan recoveries	232	207	872
Ending Balance	2,397	805	902
Consumer \| Other revolving and installment
Changes in the allowance
Beginning Balance	380	499	400
Provision for loan losses	383	(24)	276
Loan charge-offs	(572)	(308)	(429)
Loan recoveries	161	213	252
Ending Balance	$ 352	$ 380	$ 499

Amount of increase in allowance for credit loss on accounts receivable, from recovery.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (e)
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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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